Hemispheric asymmetries represent a fundamental organizational principle of sensory, cognitive, or motor processing in the brains of many animal species. This lateralization is related to left-right differences in the structural organization of neural circuits, but how these asymmetries emerge during ontogeny is still poorly understood. A much discussed issue is the relative importance of genetic and environmental factors. In a current neuroanatomical study, biopsychologists from Bochum therefore investigated how projection asymmetries develop in the visual system of pigeons. Retrograde tracing of the major ascending (tectorotundal) projections in light-exposed and –deprived pigeons indicates that light stimulation during embryonic development leads to a stronger innervation of the left side of the brain. However, light does not enhance stabilization of fibers within the left hemisphere but induces stronger pruning of projections to the less stimulated right hemisphere. These data illustrate how visual input during early development modifies connectivity pattern in both brain halves, which in turn profoundly affects lateralized sensory processing, and ultimately lateralized cognitive processes, decision-making, or behavioral control.

Letzner S, Manns M, Güntürkün O. Light-dependent development of the tectorotundal projection in pigeons. Eur J Neurosci. 2020 Sep;52(6):3561-3571. doi: 10.1111/ejn.14775. https://onlinelibrary.wiley.com/doi/10.1111/ejn.14775